This invention relates to a combustion heater for use in vehicles with a hot storage for preserving foods, etc. in a hot state, or the like, and more particularly to a combustion heater of this kind which is adapted to vaporize liquid fuel supplied to the wick, and ignite and burn a mixture of combustion air and vaporized liquid fuel within a combustion chamber.
Conventionally, a combustion heater of this kind has been proposed e.g. by U.S. Ser. No. 07/479,087 assigned to the same assignee as the present application, now abandoned. The proposed combustion heater comprises, as shown in FIG. 1, a burner cylinder 104 having a peripheral wall thereof formed with a number of air inlet holes 104b to define a combustion chamber 104a therein, a wick 106 for impregnating with liquid fuel, a wick holder 107 holding the wick 106 exposed to the combustion chamber 104a , a shaft 122 secured at one end thereof to the wick holder 107 in a manner projecting into the combustion chamber 104a, and a flange member 121 radially extending from the other end of the shaft 122 in a manner facing the wick 106.
According to the proposed combustion heater, the flange member 121 functions as follows: When combustion air radially flows straight toward the axis of the burner cylinder 104 through the air inlet holes 104b, the flowing combustion air is apt to concentrate in the diametrical centeral zone of the combustion chamber 104a so that a flame rich with air occurs in the same zone, forming excess air in the diametrical central zone as well as an unburnt gas in a peripheral zone in the burner cylinder 104. However, the excess air is guided together with the flame by the flange member 121 radially outwardly toward the peripheral zone, wherefrom it flows through a gap provided between an outer peripheral surface of the flange member 121 and an inner peripheral surface of the burner cylinder 104 while being mixed with the unburnt gas. On the other hand, when combustion air flows swirlingly into the combustion chamber 104a, the vaporized fuel in the peripheral zone in the burner cylinder 104 is pushed by the swirling combustion air to the diametrical central zone so that a flame rich with fuel occurs in the diametrical central zone, forming an unburnt gas in the diametrical central zone as well as excess air in the peripheral zone in the burner cylinder 104. However, the unburnt gas is guided together with the flame by the flange member 121 radially outwardly toward the peripheral zone, wherefrom it flows through the gap between the outer peripheral surface of the flange member 121 and the inner peripheral surface of the burner cylinder 104 while being mixed with the excess air.
The flange member 121 also serves to transfer heat to the wick 106 by conduction through the shaft 122, as well as to the opposed end face of the wick 106 by radiation, thereby enhancing the degree of fuel vaporization by the wick 106.
However, the proposed combustion heater had the disadvantage that the wick 106 has a limited effective surface area from which liquid fuel is vaporized because the shaft 122 extends through the wick 106, thereby resulting in reduced combustion efficiency.
Further, the wick 106 is held between the wick holder 107 and the burner cylinder 104 with a peripheral edge thereof abutting against an opposed open end edge of the burner cylinder 106 having a small surface area. Therefore, it is difficult to stably hold the wick 106 in place.
Another disadvantage with the proposed combustion heater is that the flange member 121 requires time-consuming machining to manufacture, causing an increased manufacturing cost.